1. Field of the Invention
The present invention relates to an improved capillary ring for a capillary-type edge bead removal system.
2. Background of the Related Art
In semiconductor device manufacturing, multiple deposition processes, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating, electrochemical plating (ECP), and/or other deposition processes, are generally conducted in a process series in order to generate a multilayer pattern of conductive, semiconductive, and/or insulating materials on a substrate. When the series is used to manufacture a multilayer device, a planarization process is generally used to planarize or polish the substrate surface between the individual layer deposition steps in order to provide a relatively flat surface for the next deposition step. When an ECP process is used as a deposition step, an edge bead generally forms proximate the perimeter of the substrate, which inhibits effective planarization processes. Therefore, an edge bead removal (EBR) process is generally conducted after an ECP deposition process is complete. The EBR process generally operates to remove unwanted edge beads deposited on the bevel or edge of the substrate during the ECP deposition process, and therefore, allows for effective planarization of the substrate surface.
Metal ECP may be accomplished through a variety of methods using a variety of metals. Copper and copper alloys are generally a choice metal for ECP as a result of copper""s high electrical conductivity, high resistance to electromagnetic migration, good thermal conductivity, and it""s availability in a relatively pure form. Typically, electrochemically plating copper or other metals and alloys involves initially depositing a thin conductive seed layer over the substrate surface to be plated. The seed layer may be a copper alloy layer having a thickness of about 2000 xc3x85, for example, and may be deposited through PVD or other deposition techniques. The seed layer generally blanket covers the surface of the substrate, as well as any features formed therein. Once the seed layer is formed, a metal layer may be plated onto/over the seed layer through an ECP process. The ECP layer deposition process generally includes application of an electrical bias to the seed layer, while an electrolyte solution is flowed over the surface of the substrate having the seed layer formed thereon. The electrical bias applied to the seed layer is configured to attract metal ions suspended or dissolved in the electrolytic solution to the seed layer. This attraction operates to pull the ions out of the electrolyte solution and cause the ions to plate on the seed layer, thus forming a metal layer over the seed layer.
During the ECP process, metal ions contained in the electrolyte solution generally deposit on substrate locations where the solution contacts the seed layer. Although the seed layer is primarily deposited on the front side of the substrate, the seed layer may be over deposited and partially extend onto the edge and backside of the substrate. As such, metal ions from the electrolyte solution may deposit on the edge and backside portions of the substrate during an ECP process if the electrolyte solution contacts these portions of the substrate having the over deposited seed layer formed thereon. For example, FIG. 1A illustrates a cross sectional view of a substrate 22 having a seed layer 32 deposited on the substrate surface 35. Seed layer 32 extends to a radial distance proximate the bevel edge 33 of substrate 22 and may be deposited, for example, with a CVD or a PVD process. A conductive metal layer 38 is deposited on top of seed layer 32, through, for example, an ECP process. As a result of the seed layer 32 terminating proximate bevel 33, an excess metal layer buildup, known as an edge bead 36, generally forms proximate the bevel 33 above the terminating edge of the seed layer 32. Edge bead 36 may result from a locally higher current density at the edge of seed layer 32 and usually forms within 2-5 mm from the edge of the substrate. FIG. 1B illustrates a similar edge bead 36, and includes an illustration of a metal layer 38 extending around the bevel 33 of substrate 22 onto backside 42. This situation occurs when the seed layer 32 extends around bevel 33 onto backside 42 and comes into contact with the electrolyte during ECP process. Edge bead 36 must generally be removed from the substrate surface before further layers may be deposited thereon or before substrate processing is complete, as edge bead 36 creates a deformity in the planarity of the substrate surface that does not facilitate multilayer device formation.
EBR systems operate to remove the over deposited seed and metal layers from the edge and backside portions of the substrate. Generally, there are two primary types of EBR systems. A nozzle-type EBR system generally rotates a substrate below a nozzle that dispenses a metal removing solution onto the edge and possibly backside of the substrate in order to remove the edge bead and over deposited metal layer. A capillary-type EBR system generally floats a substrate immediately above a plastic capillary ring configured to direct a metal removing solution dispensed on the backside of the substrate around the bevel area proximate the edge bead for removal thereof.
Although both types of EBR systems are generally effective in removing the edge bead and over deposited metal layer from the substrate, both systems suffer from inherent disadvantages. For example, in a conventional capillary EBR system, such as the system illustrated in U.S. Pat. No. 6,056,825 to SEZ Corporation, a substrate is floated face down on a substrate support member via a gas flow, which may be nitrogen, for example. The gas flow exits a substrate support surface below the substrate positioned thereon, thus acting as a gas cushion for the substrate that keeps the substrate from contacting the substrate support member. However, substrates placed in EBR systems generally have a copper sulfate liquid residue on the production surface of the substrate from previous metal layer deposition steps. Therefore, when the substrate is supported by the gas flow/cushion, the gas flow often acts to dry the copper sulfate residue, which causes staining on the production surface of the substrate. Staining is undesirable, as the electrical properties of the metal layers below the stain are degraded, which may reduce the device yield. In order to avoid staining of the production surface, the production surface may be rinsed with deionized water, for example, prior to the substrate being supported by the gas cushion. However, rinsing also presents disadvantages, as the production surface may then corrode or pit as a result of the exposure to the rinsing fluid. Further, fumes from the edge bead removal solution may contact the production surface, which may also cause undesirable pitting of the surface. Another disadvantage of capillary-type EBR systems is that the geometry of the plastic capillary ring has a substantial effect upon the EBR effectiveness. For example, if the plastic capillary ring is not completely planar, then the EBR process will be uneven around the perimeter of the substrate. This poses a significant disadvantage, as the plastic capillary ring is a common component that is removed during various types of system maintenance, and when the ring is reinstalled, often the surface is not planar as a result of various torques exerted on the plastic ring from the mounting hardware.
Therefore, there exists a need for a capillary EBR system capable of being easily dismantled and reassembled for substrate production, where the capillary ring of the EBR system is configured to maintain a desired geometry upon reassembly.
Embodiments of the invention generally provide an apparatus for removing an edge bead from a substrate. The apparatus includes a substrate support member, a plurality of mounting posts positioned along a perimeter of the substrate support member, and a rigid annular capillary ring mounted to the plurality of mounting posts. The rigid annular capillary ring includes a substantially planar upper capillary surface and is configured to maintain the substantially planar capillary surface when attached to the mounting posts.
Embodiments of the invention further provide a capillary ring for an edge bead removal system, wherein the capillary ring includes an annular ring member having a substantially planar capillary surface formed thereon, the capillary ring being manufactured from a rigid material configured to maintain the substantially planar capillary surface when installed in the edge bead removal system.